1. Field of the Invention
The present invention relates to a linear amplifier, and more particularly, to a linear amplifier capable of suppressing a reduction in bandwidth and reducing a ripple voltage by using a source follower and a local feedback loop.
2. Description of the Related Art
Recently, the demand for a technology capable of rapidly transmitting low-capacity data such as voice or characters and large-capacity data such as moving pictures has increased with the development of wireless communications technology.
A typical RF amplifier cannot rapidly transmit large-capacity data while maintaining appropriate power efficiency. As a result, a method for separating the phase component and envelope component of a signal and transmitting them to an RF amplifier has been devised. As the method, an envelope tracking (ET) method using a linear RF power amplifier and a polar method using a switching power amplifier have been mainly used.
In order to implement an envelope modulator adopting the polar method, a method using a linear amplifier, a method using a switching amplifier, or a hybrid method using the linear amplifier and the switching amplifier has been used.
Among the above-mentioned methods, the hybrid method capable of using the advantages of both the linear amplifier and the switching amplifier has been mainly used. However, as power to be supplied to the RF power amplifier from the envelope modulator is increased, the current driving capability of the linear amplifier should be increased accordingly. As a result, there are problems in that the bandwidth is reduced and the ripple voltage is increased